I do not like writing about this subject.
The reason is because by providing information on this topic only
serves to increase the fear & misconceptions in the minds of
people who don't first know how to raise plants at all, let alone in
a healthy manner.
Yosemite National Park, Yellowstone Park, and others display pure nature
at its most awe inspiring. Yet there are no gardeners trimming
weeds, spreading fertilizer, or spraying insects. When a tree dies
it is recycled by decomposition from numerous vectors.
Nature is balanced. It thrives without human meddling.I can't help you with how to care for a sick specimen barely
surviving in a city apartment.
You need to get out and go visit a
local cactus & succulent store. This is because you have to see how professionals raise
specimens indoors. I have no houseplants—all are
growing outside with fresh air, sunlight, non-chlorinated well
water.

Healthy plants don’t get sick
• Over watering, lack of proper light, crappy water, bad care, these
all makes plants sick.
• Most insects avoid the bitter alkaloids in the skin. But I’ve seen
gophers eat the roots, rats gnaw on the tips. Once through the skin
it’s a starchy vegetable to them. Grasshoppers will chew on San
Pedro tips, slugs and snails will eat the skin.
I never use chemical pesticides on San Pedro for insects! It is
unnecessary plus you’ll kill off beneficial ones such as spiders,
green lacewings, etc. Insect damage (other than normal chewing ones
such as slugs/grasshoppers) is nature’s way of recycling a plant
that is not healthy. I raise thousands of plants outside without
insect problems. The most common problems people email me about:
• They unwrapped cuttings that I ship individually wrapped in
paper. Then they lay the cuttings together—unaware this will allow
the spines to stick into each other. The result is similar to what
would happen if you had been scratched by thorns— an outbreak of
small infections/scabs. It is not insects. It is not disease. You
caused an infection that will heal if left alone.
• Black bruises are caused by mechanical damage to the plant.
Dropped during unpacking, handled roughly, bumped it, etc. The
result is the same to the plant as if you bumped yourself and had a
bruise to show for it. Leave it alone. It will heal.
• Sunburn. A plant in a small pot, with dry soil in full sun can
overheat. The skin will wrinkle and turn grey. What would happen to
you if you were stripped naked then left in full sun from morning to
night? You’d be in the hospital with severe sunburn.
• Freeze damage. Cactus cannot freeze solid, then thaw out and be
OK. Neither could you.KEY TO A HEALTHY PLANT
Visit a local plant store to ask questions. Well cared for plants do
not get sick. Use healthy soil, distilled water, morning
sun/afternoon shade, fresh air, not too much nitrogen fertilizer,
let the soil dry between watering, etc.
Cactus live just fine in nature without humans fussing over them.
Keep that concept in mind. OK? Have fun!